Artificial limbs, including leg prostheses, employ a wide range of technologies to provide solutions suitable to many differing needs. For a trans-femoral amputee, basic needs in a leg prosthesis include stability, while standing and during the stance phase of a walking gait, and mechanical compatibility with the walking (or running) gait and some manner of knee flexion during stance and swing phases of a gait.
Certain trade-offs exist between security and stability and walking or running performance (dynamic behavior). A simple, non-articulable leg (having no movable knee), for example, may provide maximum stability but does not provide for an ideal gait. Also, sitting may be awkward if a person cannot bend his knee.
For low activity users, such as the elderly or persons with other illnesses, the focus is generally more on providing security and stability than on providing walking or running performance.